The present invention relates to a tracking servo system in a disk player.
In a tracking servo system, if an information recording disk (hereinafter, simply referred to as a "disk") to be played has, for example, a scar or scratch on its recording surface, there is a possibility that a noise due to the scar will be superimposed as a high-frequency noise component on a tracking error signal when an information reading point of a pickup follows a recording track at the scar portion so that a misoperation such as a so-called track jump or the like is caused by the high-frequency noise component.
In the case where the tracking servo system has a digital servo circuit configuration, when an error signal is applied to an A/D converter, a return noise is generated in the A/D converter because of the high-frequency noise component added by the scar which cannot be removed by a low-pass filter so that a misoperation is caused in the A/D converter to thereby cause a track jump.
As a measure against such noise, conventionally, for example, as shown in FIG. 3, in a tracking servo system having a digital servo circuit configuration, a transistor Q.sub.0 is connected between a signal line L for a tracking error signal and a reference electric potential point (for example, a ground level) and a scar on a disk is detected during play of the disk by a scar detection circuit 30 having a configuration as disclosed in Japanese Patent Unexamined Publication No. Sho. 59-94248 or the like so that the transistor Q.sub.0 is turned on in response to a detection output of the scar detection circuit 30 to thereby reduce the level of the tracking error signal to a reference one.
In the conventional apparatus having such a configuration, however, there has been a disadvantage in that it is necessary to especially provide the circuit 30 for exclusive use for scar detection, and that since various kinds of scars may exist on a disk, the circuit configuration becomes a factor of increase of the cost because the circuit must detect all of such various scars. Further, there has been a disadvantage in that a predetermined processing time is taken for detecting a scar so that processing cannot be performed in real time, and therefore a track jump has been caused by the influence of the delay time.